The present invention is directed toward a safety apparatus and more particularly toward a safety apparatus which forms part of a horizontal lifeline system.
Horizontal lifelines have been employed for many years to provide fall protection for workers on elevated structures. In fact, such horizontal lifelines are required and have been mandated by safety rules and regulations in many jurisdictions. Such lifelines normally consist of a rope or cable suspended between two structures such as the vertical beams of a building or the like which may be 10, 20 or even 100 feet apart. A safety harness or safety belt is worn by a worker and a lanyard connected to the harness or belt attaches to the horizontal lifeline or cable. The end of the lanyard may include either a loop which can freely move along the length of the lifeline or it may include a pulley or the like that rolls along the line. This allows the worker to move freely along the length of the lifeline to accomplish his intended tasks. In the event that the worker losses his footing or otherwise falls, the horizontal lifeline, through the lanyard and harness or safety belt will arrest the fall and prevent the worker from suffering injury. The use of such a lifeline is described, for example, in U.S. Pat. Nos. 5,332,071; 5,458,214 and 5,598,900.
In order to function properly, the horizontal lifeline must be sufficiently taut so that the worker""s lanyard can easily move across the same and so that the lifeline can function as a steadying rail for the worker, if necessary. However, when the lifeline is sufficiently taut that the same assumes a linear or substantial linear configuration, the resistance force magnitude required to effectively withstand the load impact of a falling worker becomes theoretically exceedingly large. In the event of a fall, the construction worker ordinarily generates many times his weight in the impact force exerted by the lanyard against the cable or lifeline. Thus, the tension in the lifeline is critical since this determines the amount of sag in a lifeline which, in turn, determines the load amplification by which a vertical fall arrest force applied to the lifeline is multiplied by. Therefore, it is important to know the amount of tension applied to a lifeline. In fact, the amount of tension is frequently dictated by safety rules or regulations in many jurisdictions.
A winch or similar type device is frequently used to tension a horizontal lifeline when the same is in use. The lifeline is normally connected to one anchoring point and then passes through the winch. The winch, in turn, is connected through an anchoring line to the second anchor point. A winch-like device for tightening a horizontal lifeline is available through Fujii Denko of Japan and is described in their product brochure No. 221, the subject matter of which is incorporated by reference herein.
Because the amount of tension on the horizontal lifeline is critical and is mandated by regulation, it is important to know what that tension is and to adjust the tensioning device accordingly. This normally requires a separate tension indicator. Such devices may be placed in line with either the horizontal lifeline or the anchoring line and may be in the form of a tension gauge or the like.
It is also well known that shock absorbers in combination with horizontal lifelines are desirable to absorb the initial force placed on the anchoring devices of the lifeline. This enables controlled elongation of the lifeline under load to increase the sag angle and, therefore, reduce the amplification forces on the anchors. At the same time, this prevents shock to the fallen worker by allowing him to come to a more gradual stop in the event of a fall. Known types of shock absorbing devices are described, for example, in the three prior art patents referred to above.
Heretofore, no device has been available which accomplishes all of the functions described above. Although the shock absorber shown in U.S. Pat. No. 5,458,214 includes a tension indicating means therein for indicating the amount of tension on the lifeline, the device is somewhat complex and still lacks the additional features described above. There has, therefore, been a need for a safety apparatus for use with horizontal lifelines which combines the features of a tensioner, adjustable shock absorber and a gauge or indicator.
The present invention is designed to overcome the deficiencies of the prior art described above and provides a safety device or apparatus which is capable of tensioning a horizontal lifeline while providing an adjustable shock absorber and a gauge or indicator for indicating the amount of tension on the lifeline. In a first embodiment, the invention includes a housing which is adapted to be secured to an anchor point through an anchoring line. The free end of a horizontal lifeline passes over a pulley within the housing and around a number of rollers which are adapted to maintain the lifeline in secure contact with the pulley. A lever is utilized to rotate the pulley in order to tension the lifeline. The lever, however, is interconnected to the pulley through an adjustable disk brake which can be preset to a desired force. When the tension on the lifeline reaches its desired level, the brake slips and the lever can freely rotate.
A second series of disk brakes connected to the pulley function as a shock absorber. In the event of a fall, the initial force on the horizontal lifeline exceeds the braking force of the shock absorber brakes and the pulley can rotate through a limited number of turns. Eventually, however, the shock absorber brake slows the fall and eventually stops the same. The amount of tension on the shock absorber brake can also be adjusted to thereby control the amount of shock being absorbed. An additional brake mechanism prevents the lifeline from freely being drawn from the housing in the event of a complete failure of the mechanism thereof.
In a second embodiment of the invention, the working end of the horizontal lifeline is secured to the axle of a pulley. The previously described housing includes a grooved drum rather than a pulley. One end of a cable is secured to the rotatable drum and the length of the cable is wound around the drum, with the cable resting within the grooves. The cable then passes around the pulley and has its free end secured to the housing. The safety device otherwise, however, works in substantially the same manner as the first embodiment.